Initial support for BEAM interpreter

Author: GregMefford

interpreter/beam/beam.go

@@ -0,0 +1,135 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package beam // import "go.opentelemetry.io/ebpf-profiler/interpreter/beam"
+
+// BEAM VM Unwinder support code
+
+// The BEAM VM is an interpreter for Erlang, as well as several other languages
+// that share the same bytecode, such as Elixir and Gleam.
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+
+	log "github.com/sirupsen/logrus"
+
+	"go.opentelemetry.io/ebpf-profiler/host"
+	"go.opentelemetry.io/ebpf-profiler/interpreter"
+	"go.opentelemetry.io/ebpf-profiler/libpf"
+	"go.opentelemetry.io/ebpf-profiler/libpf/pfelf"
+	"go.opentelemetry.io/ebpf-profiler/remotememory"
+	"go.opentelemetry.io/ebpf-profiler/reporter"
+	"go.opentelemetry.io/ebpf-profiler/support"
+)
+
+var (
+	// regex for matching the process name
+	beamRegex                      = regexp.MustCompile(`beam.smp`)
+	_         interpreter.Data     = &beamData{}
+	_         interpreter.Instance = &beamInstance{}
+)
+
+type beamData struct {
+	version uint32
+}
+
+type beamInstance struct {
+	interpreter.InstanceStubs
+
+	data *beamData
+	rm   remotememory.RemoteMemory
+}
+
+func readSymbolValue(ef *pfelf.File, name libpf.SymbolName) ([]byte, error) {
+	sym, err := ef.LookupSymbol(name)
+	if err != nil {
+		return nil, fmt.Errorf("symbol not found: %v", err)
+	}
+
+	memory := make([]byte, sym.Size)
+	if _, err := ef.ReadVirtualMemory(memory, int64(sym.Address)); err != nil {
+		return nil, fmt.Errorf("failed to read process memory at 0x%x:%v", sym.Address, err)
+	}
+
+	log.Infof("read symbol value %s: %s", sym.Name, memory)
+	return memory, nil
+}
+func readReleaseVersion(ef *pfelf.File) (uint32, []byte, error) {
+	otp_release, err := readSymbolValue(ef, "etp_otp_release")
+	if err != nil {
+		return 0, nil, fmt.Errorf("failed to read OTP release: %v", err)
+	}
+
+	// Slice off the null termination before converting
+	otp_major, err := strconv.Atoi(string(otp_release[:len(otp_release)-1]))
+	if err != nil {
+		return 0, nil, fmt.Errorf("failed to parse OTP version: %v", err)
+	}
+
+	erts_version, err := readSymbolValue(ef, "etp_erts_version")
+	if err != nil {
+		return 0, nil, fmt.Errorf("failed to read erts version: %v", err)
+	}
+
+	return uint32(otp_major), erts_version, nil
+}
+
+func Loader(ebpf interpreter.EbpfHandler, info *interpreter.LoaderInfo) (interpreter.Data, error) {
+	matches := beamRegex.FindStringSubmatch(info.FileName())
+	if matches == nil {
+		return nil, nil
+	}
+	log.Infof("BEAM interpreter found: %v", matches)
+
+	ef, err := info.GetELF()
+	if err != nil {
+		return nil, err
+	}
+
+	otp_version, _, err := readReleaseVersion(ef)
+	if err != nil {
+		return nil, err
+	}
+
+	symbolName := libpf.SymbolName("process_main")
+	interpRanges, err := info.GetSymbolAsRanges(symbolName)
+	if err != nil {
+		return nil, err
+	}
+
+	if err = ebpf.UpdateInterpreterOffsets(support.ProgUnwindBEAM, info.FileID(), interpRanges); err != nil {
+		return nil, err
+	}
+
+	d := &beamData{
+		version: otp_version,
+	}
+
+	log.Infof("BEAM loaded, otp_version: %d, interpRanges: %v", otp_version, interpRanges)
+	//d.loadIntrospectionData()
+
+	return d, nil
+}
+
+func (d *beamData) Attach(ebpf interpreter.EbpfHandler, pid libpf.PID, bias libpf.Address, rm remotememory.RemoteMemory) (interpreter.Instance, error) {
+	log.Infof("BEAM interpreter attaching")
+	return &beamInstance{
+		data: d,
+		rm:   rm,
+	}, nil
+}
+
+func (r *beamInstance) Detach(ebpf interpreter.EbpfHandler, pid libpf.PID) error {
+	return nil
+}
+
+func (r *beamInstance) Symbolize(symbolReporter reporter.SymbolReporter, frame *host.Frame, trace *libpf.Trace) error {
+	if !frame.Type.IsInterpType(libpf.BEAM) {
+		log.Warnf("BEAM failed to symbolize")
+		return interpreter.ErrMismatchInterpreterType
+	}
+	log.Infof("BEAM symbolizing")
+	return nil
+}

libpf/frametype.go

@@ -49,6 +49,8 @@ const (
 	V8Frame FrameType = support.FrameMarkerV8
 	// DotnetFrame identifies the Dotnet interpreter frames.
 	DotnetFrame FrameType = support.FrameMarkerDotnet
+	// BEAMFrame identifies the BEAM interpreter frames.
+	BEAMFrame FrameType = support.FrameMarkerBEAM
 	// AbortFrame identifies frames that report that further unwinding was aborted due to an error.
 	AbortFrame FrameType = support.FrameMarkerAbort
 )

libpf/interpretertype.go

@@ -31,6 +31,8 @@ const (
 	V8 InterpreterType = support.FrameMarkerV8
 	// Dotnet identifies the Dotnet interpreter.
 	Dotnet InterpreterType = support.FrameMarkerDotnet
+	// BEAM identifies the BEAM interpreter.
+	BEAM InterpreterType = support.FrameMarkerBEAM
 )
 
 // Pseudo-interpreters without a corresponding frame type.
@@ -64,6 +66,7 @@ var interpreterTypeToString = map[InterpreterType]string{
 	Perl:    "perl",
 	V8:      "v8js",
 	Dotnet:  "dotnet",
+	BEAM:    "beam",
 	APMInt:  "apm-integration",
 }
 

processmanager/ebpf/ebpf.go

@@ -102,6 +102,7 @@ type ebpfMapsImpl struct {
 	phpProcs           *cebpf.Map
 	rubyProcs          *cebpf.Map
 	v8Procs            *cebpf.Map
+	beamProcs          *cebpf.Map
 	apmIntProcs        *cebpf.Map
 
 	// Stackdelta and process related eBPF maps
@@ -199,6 +200,12 @@ func LoadMaps(ctx context.Context, maps map[string]*cebpf.Map) (EbpfHandler, err
 	}
 	impl.v8Procs = v8Procs
 
+	beamProcs, ok := maps["beam_procs"]
+	if !ok {
+		log.Fatalf("Map beam_procs is not available")
+	}
+	impl.beamProcs = beamProcs
+
 	apmIntProcs, ok := maps["apm_int_procs"]
 	if !ok {
 		log.Fatalf("Map apm_int_procs is not available")
@@ -294,6 +301,8 @@ func (impl *ebpfMapsImpl) getInterpreterTypeMap(typ libpf.InterpreterType) (*ceb
 		return impl.rubyProcs, nil
 	case libpf.V8:
 		return impl.v8Procs, nil
+	case libpf.BEAM:
+		return impl.beamProcs, nil
 	case libpf.APMInt:
 		return impl.apmIntProcs, nil
 	default:

processmanager/execinfomanager/manager.go

@@ -18,6 +18,7 @@ import (
 	"go.opentelemetry.io/ebpf-profiler/host"
 	"go.opentelemetry.io/ebpf-profiler/interpreter"
 	"go.opentelemetry.io/ebpf-profiler/interpreter/apmint"
+	"go.opentelemetry.io/ebpf-profiler/interpreter/beam"
 	"go.opentelemetry.io/ebpf-profiler/interpreter/dotnet"
 	"go.opentelemetry.io/ebpf-profiler/interpreter/hotspot"
 	"go.opentelemetry.io/ebpf-profiler/interpreter/nodev8"
@@ -124,6 +125,9 @@ func NewExecutableInfoManager(
 	if includeTracers.Has(types.DotnetTracer) {
 		interpreterLoaders = append(interpreterLoaders, dotnet.Loader)
 	}
+	if includeTracers.Has(types.BEAMTracer) {
+		interpreterLoaders = append(interpreterLoaders, beam.Loader)
+	}
 
 	interpreterLoaders = append(interpreterLoaders, apmint.Loader)
 

support/ebpf/beam_tracer.ebpf.c

@@ -0,0 +1,37 @@
+#include "bpfdefs.h"
+#include "tracemgmt.h"
+#include "types.h"
+
+bpf_map_def SEC("maps") beam_procs = {
+  .type = BPF_MAP_TYPE_HASH,
+  .key_size = sizeof(pid_t),
+  .value_size = sizeof(BEAMProcInfo),
+  .max_entries = 1024,
+};
+
+SEC("perf_event/unwind_beam")
+int unwind_beam(struct pt_regs *ctx) {
+  static const char fmt[] = "Unwinding BEAM stack";
+  bpf_trace_printk(fmt, sizeof(fmt));
+  DEBUG_PRINT("Unwinding BEAM stack");
+
+  PerCPURecord *record = get_per_cpu_record();
+  if (!record) {
+    return -1;
+  }
+
+  int unwinder = get_next_unwinder_after_interpreter(record);
+  u32 pid = record->trace.pid;
+
+  BEAMProcInfo *beaminfo = bpf_map_lookup_elem(&beam_procs, &pid);
+  if (!beaminfo) {
+    DEBUG_PRINT("No BEAM introspection data");
+    goto exit;
+  }
+
+  DEBUG_PRINT("==== unwind_beam stack_len: %d, pid: %d ====", record->trace.stack_len, record->trace.pid);
+
+exit:
+  tail_call(ctx, unwinder);
+  return -1;
+}

support/ebpf/frametypes.h

@@ -33,6 +33,8 @@
 #define FRAME_MARKER_PHP_JIT       0x9
 // Indicates a Dotnet frame
 #define FRAME_MARKER_DOTNET        0xA
+// Indicates a BEAM frame
+#define FRAME_MARKER_BEAM          0xB
 
 // Indicates a frame containing information about a critical unwinding error
 // that caused further unwinding to be aborted.

support/ebpf/types.h

@@ -328,6 +328,7 @@ typedef enum TracePrograms {
   PROG_UNWIND_RUBY,
   PROG_UNWIND_V8,
   PROG_UNWIND_DOTNET,
+  PROG_UNWIND_BEAM,
   NUM_TRACER_PROGS,
 } TracePrograms;
 
@@ -477,6 +478,11 @@ typedef struct V8ProcInfo {
   u8 codekind_shift, codekind_mask, codekind_baseline;
 } V8ProcInfo;
 
+// BEAMProcInfo is a container for the data needed to build a stack trace for a BEAM process.
+typedef struct BEAMProcInfo {
+  u32 version;
+} BEAMProcInfo;
+
 // COMM_LEN defines the maximum length we will receive for the comm of a task.
 #define COMM_LEN 16
 

support/types.go

@@ -24,6 +24,7 @@ const (
 	FrameMarkerPerl     = C.FRAME_MARKER_PERL
 	FrameMarkerV8       = C.FRAME_MARKER_V8
 	FrameMarkerDotnet   = C.FRAME_MARKER_DOTNET
+	FrameMarkerBEAM     = C.FRAME_MARKER_BEAM
 	FrameMarkerAbort    = C.FRAME_MARKER_ABORT
 )
 
@@ -37,6 +38,7 @@ const (
 	ProgUnwindPerl    = C.PROG_UNWIND_PERL
 	ProgUnwindV8      = C.PROG_UNWIND_V8
 	ProgUnwindDotnet  = C.PROG_UNWIND_DOTNET
+	ProgUnwindBEAM    = C.PROG_UNWIND_BEAM
 )
 
 const (

tracer/types/parse.go

@@ -22,6 +22,7 @@ const (
 	RubyTracer
 	V8Tracer
 	DotnetTracer
+	BEAMTracer
 
 	// maxTracers indicates the max. number of different tracers
 	maxTracers
@@ -35,6 +36,7 @@ var tracerTypeToName = map[tracerType]string{
 	RubyTracer:    "ruby",
 	V8Tracer:      "v8",
 	DotnetTracer:  "dotnet",
+	BEAMTracer:    "beam",
 }
 
 var tracerNameToType = make(map[string]tracerType, maxTracers)